The present invention relates generally to imprinting, and more particularly to a method of imprinting an image on a soft surface such as: a handbag; backpack; appointment book; carrying bag; sports bag; gym bag; briefcase; luggage; cooler; beverage holder; lunch box; a nylon, polyester, or cotton article; a soft-sewn article; polyvinyl chloride (PVC) and PVC derivatives.
The contents of each U.S. patent or other reference, if any, cited in this application, are hereby incorporated herein by reference.
Silk screening and other imprinting processes are common for transferring images onto items such as T-shirts, etc. For example, in a direct screening process, wet ink is forced through a screen onto the target surface. The ink has some inherent adhesive properties, but nonetheless may bleed causing fuzzy image edges. In addition, known direct screening processes are not suitable for certain target materials such as PVC and PVC derivatives. For multi-color images, typically multiple screens are used successively. In such instances, problems may arise due to misalignment of a subsequent screen, resulting in a misaligned image and therefore a non-desirable image on the target surface. Further, the multi-color process may require extra waiting time to allow one color to dry before a subsequent color is applied, or else the wet ink from different colors may bleed together.
In known heat transfer methods, an image is applied to heat transfer paper with ink, and is then transferred to the target surface through heat and pressure. Again, the ink has some inherent adhesive properties, but problems arise which cause the transferred image to separate from the target surface under various environmental conditions. Also, known heat transfer methods are not suitable for certain target materials such as PVC and PVC derivatives.
Accordingly, there is a need for an alternative and improved method of imprinting images on soft surfaces, to overcome the above-identified drawbacks, and to provide a more durable and more accurate image.
The present invention describes a method of imprinting images on a soft surface, such as: a handbag; backpack; appointment book; carrying bag; sports bag; gym bag; briefcase; luggage; cooler; beverage holder; lunch box; a nylon, polyester, or cotton article; a soft-sewn article; polyvinyl chloride (PVC) and PVC derivatives. The method of the present invention uses an ink compound comprising ink and aromatic polyisocyanates, to provide a more durable image on the target surface as described herein.
Once a film positive of the image is created, a screen is developed as is known in the art. A press is set up which may include custom rigging to accommodate the particular dimensions and other characteristics of the article embodying the target surface. A sheet of heat transfer paper, on which the image is initially provided, is cut to desired dimensions if necessary. The desired dimensions may include calculations to accommodate multiple copies of the image on a single sheet of heat transfer paper, to be subsequently separated into individual images.
To prepare the ink compound, the ink of desired color is mixed with aromatic polyisocyanates in desired proportions, typically in a ratio of approximately 2-40 parts ink to 1 part aromatic polyisocyanates. The ink may be polyvinyl chloride plastisol silk screen ink, commonly available. The ink compound is then used to screen a reverse of the target image onto the image side of the heat transfer paper. The reverse image is then coated with dry powder, such as thermoplastic co-polyamides. The heat transfer paper with the ink compound and powder thereon is then heated/cured, typically in an oven for 2-30 seconds at 100-350 degrees Fahrenheit. If multiple images have been created on a single sheet of heat transfer paper, the multiple images are then separated into individual images by cutting, shearing, etc.
The image has now been prepared for application onto the target surface, typically the soft-sewn surface of a consumer product/article such as a handbag or the like. The product is secured to an apparatus on a heat/pressure press such as a heat stamping machine or a heat transfer machine. The apparatus is typically custom-designed to accommodate the desired product. The image is then applied to the target surface by pressing the heat transfer paper (image side down) onto the surface at the desired location at suitable temperatures and pressures for a suitable duration. Typically, the temperature, pressure, and time variables are in the range of 100-400 degrees Fahrenheit, 30-120 pounds per square inch (psi), and 2-40 seconds, respectively. During the application process, the temperature and pressure variables need not be constant for the entire duration.
The process thus described results in the image on the target surface being the reverse of the image as viewed from the image side of the heat transfer paper after originally being placed thereon. However, as used herein, xe2x80x9cimagexe2x80x9d refers to a visually identifiable image, regardless of orientation. For example, once the ink compound is applied to the heat transfer paper as described herein, an xe2x80x9cimagexe2x80x9d appears on the heat transfer paper. Similarly, once powder is applied thereto, the xe2x80x9cimagexe2x80x9d still appears, though it may appear powdery or coated. Similarly, once the ink compound with the powder is transferred from the heat transfer paper to the target surface, the target surface contains the xe2x80x9cimagexe2x80x9d, even though the image on the target surface is the reverse of the image as it may have been viewed from the image side of the heat transfer paper prior to application to the target surface. xe2x80x9cReverse imagexe2x80x9d and similar terms are used herein merely to facilitate understanding of the process. Thus, xe2x80x9cimagexe2x80x9d is not to be limited to any particular orientation thereof, though a particular reference to an image may be understood to be the reverse of another reference to the same image depending on the relative relation of each of the references to each other during the process as described herein.
After the image is applied to the target surface, the product embodying the target surface is disengaged from the apparatus, and set to cool. The heat transfer paper is then removed from the product, typically by peeling the heat transfer paper away therefrom. The surface with the image thereon may then be heated at suitable temperatures for a suitable duration. Typically, the temperature and time variables are in the range of 220-400 degrees Fahrenheit, and 10-60 seconds respectively. The specific values of those variables may depend on the characteristics of the product, including material composition, thickness, and overall dimensions, and for any particular product may be determined by a minimal amount of trial and error. This final heating is typically performed in a curing tunnel. This final heating results in the ink compound fusing to the target surface, because elasticizers in the ink compound/powder combination are loosened and activated, and molecules on the target surface are separated, all of which facilitates the image (embodied in the ink compound/powder combination) fusing to the target surface. In addition, the final heating causes small traces of excess powder to evaporate. The product with the image thus imprinted thereon is then ready to cool, pack, and distribute.
For application of a multi-color image, desired colored inks are used to form multiple ink compounds, and each color is applied to the heat transfer paper independently such that together they form the desired multi-color image with little or no overlap between the individual colors. Backer film may be used to ensure fine lines and colors. The heat transfer paper is initially heated prior to application of the first color, to shrink the paper thus avoiding further shrinkage between color applications which might otherwise cause misalignment of the various colors with respect to the overall multi-color image. Additionally, the heat transfer paper is heated after application of each color, and the powder is applied preferably only after all colors have been applied and heated.
The invention as described herein thus provides an alternative and improved method of imprinting an image on a soft surface, which overcomes the drawbacks of known methods, and provides a more durable image on the target surface. Further objects and advantages of the present invention are discussed in the detailed description which follows, read in conjunction with the drawings: